1. Field of the Invention
This invention relates to an intake and exhaust valve control system for internal combustion engines. More specifically, the invention is concerned with such a system including a primary control and a variable secondary control.
2. The Prior Art
Conventionally, exhaust and intake valves are opened and closed in timed relationship by a system including a cam shaft and a set of poppet valves, rocker arms, valve lifters and a myriad of associated parts. A given camshaft produces a given valve timing sequence, i.e., the intake and exhaust valves will open at given times, remain open for a predetermined time and close at given times. Changing valve timing in such a system requires the substitution of a new, differently ground cam shaft.
During a search for patents related to the instant invention, the following U.S. Patents were noted: U.S. Pat. Nos. 1,273,002, 1,624,992, 1,665,421, 1,754,647, 1,781,176, 1,818,527, 1,873,012, 1,899,743, 1,922,678, 1,934,710, 2,028,138, 2,074,487, 2,113,519, 2,265,171, 2.373,924, 2,409,350, 3,990,423, 4,098,238 and 4,201,174. U.S. Pat. Nos. 2,575,394, 2,874,686, 3,277,696 and 3,439,960 are the most recent cited references in respect of U.S. Pat. No. 4,201,174.